1. Field of the Invention
The present invention relates to a guiding mechanism for flat cable, and more particularly to a guiding mechanism for keeping flat cable connected between two traveling modules of an image scanning device.
2. Description of the Prior Art
In various kinds of optical devices or electric appliances (such as image scanner, photo copier, test instrument, etc.), two traveling modules are often equipped therein. For example, as shown in FIG. 1, it is a perspective view of a conventional optical image scanning device, showing that a focusing lens 2, a protective cover 3, a pair of corresponding guide rods 4a, 4b, and two movable traveling modules 5a, 5b are arranged in the housing 1 of the conventional optical image scanner.
The guide rods 4a, 4b serve as a guiding mechanism for guiding two traveling modules 5a, 5b. The first traveling module 5a carries a light tube as a light source for the image scanning device, while the second traveling module 5b carries a set of reflection mirrors for reflecting the light projected from the light source. During scanning, a document to be scanned is placed on a document positioning plate of the scanner. It is known that the document positioning plate is a plane surface made, for example, from glass or other light transmittable, substantially rigid material for supporting a document to be scanned. The light tube of the first traveling module 5a projects a light toward the document and then the light is reflected by the reflection mirror of the second traveling module 5b. The first and second traveling modules 5a, 5b are arranged to achieve a necessary scanning optical path during scanning. Typically, the first and second traveling modules 5a, 5b may be moved by a conventional driving motor via a transmission rope (not shown). In general, the ratio of the speed of the first traveling module 5a to the speed of the second traveling module 5b is 2:1.
Normally, a circuit board 7 is mounted on a side wall of the first traveling module 5a. One end of a flat cable 6 disposed with a connector 61 is electrically connected to the circuit board 7. The other end of the flat cable 6 extends to connect with a fixed position 11 of the base plate 12 of the housing or a protective cover 3 mounted on the housing 1. The protective cover 3 contains therein a circuit board and other relevant electronic components.
The flat cable 6 generally has a certain flexibility. However, the minimum curvature radius and the tolerable number of bending times of the flat cable 6 are limited. Since the traveling modules need to frequently move left and right, the flat cable 6 will be repeatedly bent. In the case of too large of a bending angle, the flat cable 6 may be broken or damaged.
Moreover, the width of the existing flat cable is narrower and narrower (the number of pins is reduced) with longer length (such as used in scanning of A3 size document). Therefore, during the movement of the traveling modules, the flat cable is likely to curve and touch other components arranged in the housing of the image scanning device or even be rolled into the traveling mechanism. In addition, the flat cable may swing left and right during movement of the traveling modules. These all lead to lowered reliability and shortened usable life of the scanner.